1. Field of Invention
This invention relates generally to the display of television images, and in particular to the realistic simulation of three-dimensional images.
2. Prior-Art
Three-Dimensional Displays—Cathode Ray Tubes
After two-dimensional (2-D) television was invented by Philo T. Farnsworth in 1927 in San Francisco, Calif., U.S.A., subsequent developers have sought ways to provide three-dimensional (3-D) television. In U.S. Pat. No. 3,555,349 (1971), Muntz teaches a cathode ray tube (CRT) containing numerous, transparent imaging planes. Each plane comprises zones and individual phosphor picture elements which are addressed by an electron beam. Each plane is transparent to the electron beam and all planes are impinged simultaneously by it. However the elements of only a single plane fluorescence at a time. Fluorescence in all other planes is quenched by a radio frequency electric field. Thus a true 3-D image is presented to the viewer.
In U.S. Pat. No. 3,878,329 (1975), Brown teaches a cathode ray orthoscopic image tube. This tube comprises a wide-beam electron gun, magnetic horizontal and vertical deflection apparatus adapted for digital control, an electromagnetic dynamic electron beam focusing arrangement, a phosphor layer, an aperture lens array, a fiber optic face plate and a fly's eye lens array. Brown's apparatus presents a simulated 3-D image to the viewer.
While both Muntz and Brown can provide a 3-D image, they used custom-designed CRTs that required extraordinary care and precision in manufacture, are complex and expensive to make, are fragile, and require complex electronic circuitry in order to function as taught. In addition, since Brown displays all parts of the image at the same depth, the viewer does not see a true 3-D image.
Cathode Ray Tube Combined with External Apparatus
In U.S. Pat. No. 6,005,608 (1999), Chakrabarti teaches a true 3-D display apparatus for use without special 3-D glasses. The apparatus includes an ordinary CRT, a screen, a screen moving assembly, an imaging system, a focusing system, and a control system for receiving a signal representative of a 3-D image and separating the signal into a series of two-dimensional (2-D) representations.
In use, the control system causes the CRT to present a focused, first 2-D image to the screen, moves the screen to a second position, causes the CRT to present a focused, second 2-D image to the screen, and so forth until all 2-D representations of the 3-D image have been shown. The process then repeats.
While this apparatus presents a true 3-D image to the viewer, its mechanical nature imposes a speed-size trade-off, i.e., while a relatively small system could conceivably operate at standard video rates, a relatively large system would require a great deal of mechanical effort to produce 3-D images at a 25–30 Hz rate, as required to prevent flicker when seen by the human eye. Further, the belts, pulleys, and motor of the apparatus add significant cost and would likely require frequent maintenance. While this system displays portions of the image at different depths, it is not static and requires a prohibitively expensive and awkward mechanical arrangement.
Multi-Planar Volumetric Display System
A variation on the above system is taught by Sullivan in published U.S. patent application U.S. 2002/0130820. Instead of projecting a series of sections of a 3-D images on a mechanically moving screen, Sullivan employs a series of fixed-position liquid crystal screens oriented parallel to one-another and spaced by a predetermined amount. Each screen is either transparent or translucent. A controller coordinates 2-D image slices projected by a projector through the series of screens. A first, most distant image section is projected and the screen nearest the projector is rendered translucent, while the remaining screens are rendered transparent. Next, a second, next-most-distant image section is projected, and the screen nearest the projector is rendered transparent, the second-nearest screen is rendered translucent, and all remaining screens are transparent. This sequence continues until all sections of the image have been displayed, whereupon it repeats. Various other embodiments employ this basic component of the system.
While this system displays a true 3-D rendering of an image, it is relatively expensive, and requires sequential display of different-depth images.
Flat Panel Liquid Crystal Displays
In U.S. Pat. No. 6,040,807 (2000), Hamagishi et al. teach a 3-D liquid crystal display (LCD) comprising a flat light source, a vertical striped filter having slits, barriers for screening light from the light source, and a transmission-type display panel having left eye and right eye pixels formed alternately within. Hamagishi's device presents a simulated 3-D image to the viewer. Different parts of the image are displayed at the same depth.
While this arrangement of elements produces a 3-D image, it employs a technology and structure which are costly to prepare, less adaptable to various light sources, and do not present a true 3-D image.
Viewscreen Add-On for Various Display Types
In U.S. Pat. No. 6,157,402 (2000), Torgeson teaches a screen assembly for producing stereoscopic television (TV) images. His screen can be used with a projection LCD, plasma, and other kinds of displays that produce video pictures by scanning techniques. The TV image source image is applied to the back side of the screen assembly, and is viewed from the front side. Different parts of the image are displayed at the same depth.
As with Hamagishi's system, this arrangement of elements does produce a 3-D image. However it employs a technology and structure which are again costly to prepare, less adaptable to various light sources, and does not present a true 3-D image.
Fiber Optic Add-On for Video Projectors
In U.S. Pat. No. 6,128,132 (2000), Wieland et al, teach a 3-D viewing system comprising one or more light sources generating at least two views of an image, a slit-type barrier screen, at least one light-transmitting element coupled to the barrier screen, and a signal generator. The preferred light transmitting element is a fiber optic array.
In this apparatus, light is conveyed from a projector to one end of a fiber optic element array. At the other end of the fiber optic array, light from the fiber optic elements terminates on a single, planar screen containing slits which separate the right eye and left eye views.
This system produces a simulated 3-D image since the image is displayed on a 2-D screen surface. All parts of the image are displayed at the same depth.
Objects and Advantages
Accordingly, one object and advantage of the present invention is to provide an improved method and apparatus for presentation and viewing of 3-D television images. Other objects and advantages are to provide an inexpensive and simple means for obtaining 3-D image information from an ordinary TV display, which has no moving parts, can be made in any size, provides a true 3-D image by displaying parts of the image at different depths, does not require special viewing glasses, and is rugged.
Additional objects and advantages will become apparent from a consideration of the drawings and ensuing description.
Separation of Images According to Depth—FIG. 1
FIG. 1 shows a prior-art 3-D system 60. Images from an image source 50 are supplied in individual planes which are sorted according to depth. These images can be computerized animations, drawings with elements separated in planes according to depth, overlaid photographs of objects taken at different depths, and the like. For example, in the case of computerized animations, a character moves from far to near by appearing in successive planes, with each plane nearer to the viewer. These planes are uniquely identified by computer coding and supplied to a computer 105. Such a sorted image is known in the animation art and in other arts. Computer 105 can create the illusion of depth on a prior-art screen 100 by overlaying the images such that the nearer images lie on top of the farther images. Alternatively, computer 105 can cause individual planes to be displayed separately on a prior-art screen 110 as images 115–130.
Image source 50 can be a computer program. Computer software, such as sold under the mark “Canvas” by ACD Systems of Victoria, British Columbia, permits placement of objects according to their perceived depth. Individual layers of objects are superimposed in a 2-D view, such as shown on screen 100. Objects are thus represented in groups as shown in screen 100, with the nearest object obscuring the next-nearest, and so forth. Objects can also be shown individually according to their true depth, as shown in screen 110 by simply arraying individual layers across screen 110. In this example, screen 110 is divided into sections, with section 115 displaying the nearest objects, section 120 displaying near-intermediate distance objects, section 125 displaying far-intermediate distance objects, and section 130 displaying the farthest objects. More or fewer sections can be used, as required.
Another such program is sold under the mark “Director” by Macromedia, Inc. of San Francisco, Calif., U.S.A. The language used in this program is called “LINGO”. This program permits images on a PC monitor to be divided into four sections, with each section associated with a predetermined depth in an image.